1. Field of the Invention
The present invention relates to a plate-link chain for a belt-driven conical-pulley transmission. The chain has a large number of link plates that are articulatingly connected with each other by rocker members. The link plates are positioned one behind the other transversely to the longitudinal direction of the plate-link chain, and are offset from each other in the longitudinal direction of the chain and partially overlap each other. The chain has a plurality of link plates of two different lengths in the longitudinal direction of the chain, with openings to receive the rocker members.
2. Description of the Related Art
A plate-link chain of the type described herein is made up of a large number of link plates and rocker members, the rocker members also being referred to as pegs or pins, and also being known as rocker hinges.
The link plates for forming such a plate-link chain are selected from two types of plate links, namely one known as a short plate link and one known as a long plate link.
The plate-link chain thus formed is used to transmit pulling force between two conical disk pairs of a belt-driven conical-pulley transmission. The transmission of force between the conical disk pairs and the plate-link chain is friction-based. That means, in other words, that ends of the rocker members between the conical disk pairs are subjected to high normal forces, in order to be able to build up the necessary frictional force, allowing for the coefficient of friction between the rocker member ends and the surfaces of the conical disk pairs.
As the rocker members enter the space between the conical disk pairs, the entry of the rocker members produces an entry impact, which is perceptible externally as noise level. To attenuate that phenomenon, plate-link chains with so-called random pitch have already become known, in which the pitch between the individual links of the plate-link chain is not constant over the length of the plate-link chain, but varies. That makes it possible to achieve a smoothing of the entry noise, so that the entry noise is no longer acoustically dominant in the foreground.
FIG. 1 of the drawings shows a known plate-link chain according to the so-called three-plate structure. Reference numeral 10 designates short link plates, viewed in the longitudinal direction of the plate-link chain, while reference numeral 22 designates long link plates, viewed in the longitudinal direction of the plate-link chain. In the schematic representation shown in FIG. 1, reference numeral 12 designates a pin; in reality it is the center of a pair of rocker members made up of two rocker members 14, 16, as shown in FIG. 2 of the drawings.
TK designates a short pitch, while TL designates a long pitch. The pitch T is the distance between the centers of two adjacent pins 12 or of two rocker member pairs 14, 16.
The plate-link chain shown in FIG. 1 of the drawings has become known on the basis of DE 10 2004 007 100. That known plate-link chain has already proven itself very well in use. Analyses of used plate-link chains of that type to determine their wear performance have shown that they are subject to width wear or edge wear in the region of the rocker members, which wear is higher the greater the effective pitch of the plate-link chain. The reason for that is that the greater the pitch, the greater is the normal force impressed on the ends of the rocker members. A higher normal force, in turn, causes greater deformation, and hence greater slippage between the rocker members and the conical disks. The wear performance described above as a function of the pitch length must therefore be seen as a consequence of the frictional power that is dissipated in the pin-disk contact.
The wear performance of the rocker members has an influence on the service life of the belt-driven conical-pulley transmission, so that reducing the end wear of the rocker members contributes to prolonging the service life of the transmission.
Starting from that point, an object of the present invention is to provide a plate-link chain that exhibits improved wear performance.